LECTURE NOTES ON GROUND IMPROVEMENT TECHNIQUES

1 LECTURE NOTES . ON. GROUND IMPROVEMENT TECHNIQUES . (A60127). III B. Tech - II Semester (JNTUH-R15). Prepared By Dr. Kavita Singh Associate Professor Ms. J. Hymavathi Assistant Professor, Department of Civil Engineering INSTITUTE OF AERONAUTICAL ENGINEERING. (Autonomous). DUNDIGAL, HYDERABAD - 500 043. UNIT-1. Introduction to Engineering GROUND Modification. The Need for Engineered GROUND IMPROVEMENT : As more and more land becomes subject to urban or industrial development, good construction sites and borrow areas are difficult to find and the soil IMPROVEMENT alternatives becomes the best option, technically and economically. Where a project encounters difficult foundation conditions, possible alternative solutions are: 1. Avoid the particular site.

2 Relocate a planned highway or development site. 2. Design the planned structure accordingly. Some of the many possible approaches are to: - Use a raft foundation supported by piles, - Design a very stiff structure which is not damaged by settlement, - Or choose a very flexible construction which accommodates differential movement or allows for compensation. 3. Remove and replace unsuitable soils. Removing organic topsoil, which is soft, compressible, and volumetrically unstable. This is a standard precaution in road or foundation construction. 4. Attempt to modify the existing GROUND Objective of GROUND IMPROVEMENT TECHNIQUES The most common traditional objectives include IMPROVEMENT of the soil and GROUND for use as a foundation or construction material.

3 The typical Engineering objectives have been: 1) Increasing shear strength, durability, stiffness. And stability: 2) Mitigating undesirable properties (eg. Shrink/ swell potential, compressibility, liquefability 3) Modifying permeability, the rate of fluid to flow through a medium; and 4) Improving efficiency and productivity by using methods that save time and expense, The engineer must take a determination on how best to achieve the desired goals required by providing a workable solution for each project encountered. GROUND IMPROVEMENT methods have provided adverse choice of approaches to solving these challenges. Factors affecting choice of IMPROVEMENT method 1. Soil type : this is one of the most important parameters that will control what approach or materials will be applicable to only certain types of soil types and grain sizes 2.

4 Area , depth and location of treatment required- many GROUND IMPROVEMENT methods have depth limitations that render them unsuitable for applications for deeper soil horizons. 3. Desired/required soil properties- obviously, different methods are use to achieve different engineering properties, and certain methods will provide various levels of uniformity to improved sites. 4. Availability of materials- Depending on the location of the project and materials required for each fesible GROUND improvements approach. 5. Availability of skills, local experience, and local preferences- While the engineer may possess the knowledge and understanding of a preferred method. 6. Environmental concerns- With a better understanding and a greater awareness of effects on the natural environment, more attention have been placed on methods that assure less environmental impacts.

5 7. Economics- when all else has been considered, the final decision on choice of IMPROVEMENT method will often come down to the ultimate cost of a proposed method, or cost will be the deciding factor in choosing between two or more otherwise suitable methods. Identifying your soil type Soils can be identified in to their general types by the way they feel and respond to Pick up a handful and squeeze it together. Sand feels gritty and the grains do not stick together when squeezed. Loam feels velvety or flour-like when dry and forms a weak ball shape when wet which crumbles apart when dry. Clay feels sticky, but goes smooth when rubbed. Chalk will have large lumps in it and be hard to mould. How to work with your soil The most important thing is to identify your soil type and work with it, remember the golden rule All soil types have their good points and can be improved.

6 Even the best loam soils will benefit from additional organic matter. Heavy, Clay soil This holds water, but also bakes dry in the summer. However, clay is very good at holding nutrients and moisture and very fertile as long as you can break it down with the addition of organic matter and grit. This will enable the roots of plants to get through to the nutrients more easily and of course make planting less back breaking for you. Try and avoid walking on the soil too much as this will compact it to a hard pan. Sandy soil It loses water very quickly being particularly free-draining. However, you can improve both of these factors with the addition of organic matter and soil improver and of course, many plants thrive in a free-draining soil. It also warms up quickly in the spring.

7 Chalky This is alkaline so will not suit plants that require ericaceous soil. Some soils contain large clumps of chalk; others are a mixture of chalk and clay. It is normally free draining, but may be low in nutrients so as with the other soils the addition of organic matter will help with both the structure and nutritional content of the soil. Normal It retains moisture without impeding drainage, captures nutrients and allows oxygen to circulate. It normally contains equal quantities of sand, clay, silt, and organic matter. Loam, Sand & Silt Soil Identification Soil type affects drainage. Many plants are quite picky about the type of soil in which they live. Therefore, identifying your garden's kind of soil will help you know whether particular plants will do well in your garden without soil amendment or with soil amendment, or if you should just skip using those plants altogether.

8 Sandy Soil Most people associate sandy textures with those they feel between their toes at the beach, and the feeling is similar in sandy soil. Its particles are the largest of all the soil particle types, ranging from to millimeters at the small end and 1 to 2 millimeters at the large end. That factor gives wet or dry sandy soil a grainy texture when you rub it between your fingers, and it makes the soil light and crumbly even when you try to stick it together in your hand. Sandy soil drains very quickly. Silt Soil Many people think of loam as the intermediate between sand and clay, but midsized soil particles are referred to as silt. Silt soil is fine and feels almost floury to the touch when dry. When wet, it becomes a smooth mud that you can form easily into balls or other shapes in your hand.

9 When silt soil is very wet, it blends seamlessly with water to form fine, runny puddles of mud. Silt particles are very small, between and millimeters, which results in their very smooth texture. Silty soil drains well but not as quickly as sand. Clay Soil Clay particles are the finest of all the soil particles, measuring fewer than millimeters in size. They stick together readily and form a sticky or gluey texture when they are wet or dry. When you gather clay soil into your hand, you can readily shape it into whatever form you want. It will form a ball that doesn t break when squeezed, or a thin, flexible ribbon when pressed between your thumb and forefinger. Loam Soil Loam is not its own particle type but a designation for soils containing certain combinations of other particles.

10 The way the other particles combine in the soil makes the loam. For instance, a soil that is 30 percent clay, 50 percent sand and 20 percent silt is a sandy clay loam, with the soil types before "loam" listed in the order their particles are most dominant in the loam. The labels clay loam, silt loam and sand loam are used to refer to soils that are composed predominantly of those ingredients. Insitu laboratory test for problematic Soils In Situ and Laboratory Testing ESG's (Environmental, Social and Governance) geotechnical division offers a wide range of in situ and laboratory-based testing methods for the measurement of soil and rock stiffness parameters. In recent years the importance of soil and rock stiffness parameters in geotechnical engineering design has been increasingly recognized, driven in part by the requirements of EC-7.